Method of dressing grinding wheels



Jan. 28, 1969 J KUENSTLE ET AL 3,424,566

METHOD OF DRESSING GRINDING WHEELS Filed April 15, 1965 Sheet of 2 DIAFORM lo GRINDING wHEEL 32 (FIG. 2)

I FORM LAPPING WHEEL 3 WITH DRESSED GRINDING wHEEL 32' (FIG. 3)

FORMED LAPPING WHEEL f' 40 36' SET UP 8 ALIGNED WITH ABRASIVE WHEEL 48 I6 (FIG. 4)

APPLY RouGH APPLY FINIsH J 44 LAPPING GRIT I LAPPING GRIT $16.3

(FIG.5) (FIG. 5)

I 20 GRIND ABRASIVE WHEEL 4a CONTOUR 0N CHALK 62 (FIG. 6) 32 22 I CHALK FORM 62 I INSPECTED TO CHECK ACCURACY 44 OF ABRASIVE WHEEL 48' I ABRASIVE wHEEL 48' j READY FOR usE (FIG. 8)

' 52 I, 54 52 54 INVENTOIS FIG. 4A I JOSEPH F KUENSTLE a JOHN E. RosEN 52 v 4s BY B N 50 ,I WLATTORNEYS Jan; 28, 1969 J. F. KUENSTLE ETAL 3,424,565 METHOD OF DRESSING GRINDING WHEELS Filed April 15-, 1965 Sheet INVENTORS JOSEPH F KUENSTLE 8 JOHN E. ROSEN j I n 01mm Mm ATTORNEYS Patented Jan. 28, 19-69 METHOD OF DRESSING GRINDTNG WHEELS Joseph Franz Kuenstle and John Emanuel Rosen, Seattle,

Wash., assignors to Continental Can Company, Inc.,

New York, N.Y., a corporation of New York Filed Apr. 15, 1965, Ser. No. 448,520

US. Cl. 51293 Claims Int. Cl. 324d 11/00, 17/00 ABSTRACT OF THE DISCLOSURE A method of forming diamond grinding wheels to a predetermined shape wherein the abrasive particles, being retained about the periphery of the wheel in a bonding material, drop out due to a removal of the bond about the particles. A form wheel, configured to the desired contour of the finished grinding wheel, is brought close to, but not touching, the rotating grinding wheel and a lapping compound is applied between the two wheels. The rotary motion of the grinding wheel is imparted to the form wheel through the medium of the lapping compound. The compound attacks the bonding material such that certain of the diamonds fall out leaving a contoured wheel shaped to the predetermined configuration of the form wheel.

This invention relates to a method of forming abrasive wheels and more specifically to a method of dressing diamond grinding wheels wherein the diamond wheels retain their sharp grinding surfaces for extended periods of time.

In many industries, such as the can manufacturing industry, it is customary to use replaceable tools of hard substances which are employed to sever and form millions of sheet metal elements into the desired sizes and configurations. These tools are expensive to construct and it requires considerable time to replace the tools when they are no longer serviceable.

In the field of container making it is desirable to be able to produce container components within precise limits and be able to reproduce the container components repetitively over extended periods of operation. The life of the replaceable tools has been undesirably short, thus making tool replacement necessary at frequent intervals. It has been proposed to make the tools of a very hard material, such as tungsten carbide, in order to obtain extended tool life. In order to make the tools from tungsten carbide, it is necessary to start with a sintered ingot of the tungsten carbide material and to then grind the ingot with diamond grinding wheels into the final tool shape. The previously used tool materials were much softer than the later developed tungsten carbide tools and could be ground into the desired tool shapes by means of the usual aluminum oxide grinding wheels.

In order to accurately form certain of the contours into the tungsten carbide machine tools, it is necessary that the diamond grinding wheels used to form the tools be provided with the same contours about their peripheral surfaces. Little difiiculty is encountered in providing such contours in aluminum oxide grinding wheels, but, until the present invention, no satisfactory economical way of accurately cotouring diamond grinding wheels was available. Accordingly, as to be hereinafter described, the initial step in forming the diamond wheel is to provide the desired contours in an aluminum oxide or other grinding wheel.

The diamond grinding wheels or wheels of other material which are formed in the practice of the present invention, are of metal or other suitable material and are surfaced about their periphery with a thin layer of resin or soft metal bonding material which positions and holds the diamond dust in place. In the initial manufacture of the diamond wheels, the manufacture can only approximate the contour desired by the customer. Accordingly, after the wheel is purchased, it is necessary to dress the wheel into the desired contour. It has been found that the diamond wheel could not be dressed by means of the single diamond cutter of the pantographic diaforming dressing apparatus usually employed as could the aluminum oxide grinding wheel.

In the past, diamond grinding wheels have been formed by a type of brute force procedure. As taught by one example of the prior art, a dressing wheel is brought into contact against a grinding wheel; the grinding wheel being the wheel which it is desired to shape. The dressing wheel is rotated at the same peripheral velocity as the grinding wheel. The dressing wheel is brought into such extreme pressure contact with the grinding wheel that the particles of the grinding wheel are crushed and loosened in accordance with the contour of the dressing wheel. Similar teachings of the prior art disclose methods for truing diamond grinding wheels wherein a conventional type of grinding wheel is utilized. The diamond grinding wheel is rotated at a high peripheral velocity, which velocity approaches the velocity at which te diamonds would be loosened from the diamond grinding wheel by centrifu gal force. The grinding Wheel is rotated at a much lesser peripheral velocity and during the relative movement of the grinding wheel with respect to the diamond wheel, the diamonds are forced from their mountings in a crushing action.

It will be intuitively clear that the forming of vary hard abrasive grinding wheels of the prior art left a lot to be desired. For example, the removal of the diamonds or other very hard abrasive particles was accomplished through extreme pressure contact between the forming wheel and formed wheel so that the abrasive particles were crushed and cracked in order to facilitate their removal from the formed Wheel. Understandably, the peripheral surface of the formed wheel then becomes somewhat smooth in that the abrasive particles of the wheel forming the outermost peripheral surface, have become rounded or shattered and do not present an active cutting surface. In the practice of the present invention, the sharp edges and corners of the diamonds or other abrasive material are left intact in that the forming of the wheel is accomplished through a removal of the resin or metal bond which retains the diamonds on the diamond wheel, so that the diamonds are undermined and fall out. The particles are in no way crushed or splintered.

Accordingly, it is the principal object of the present invention to improve the method for forming abrasive wheels.

It is a further object of the present invention to provide a method for forming an abrasive wheel which has an extended useful abrasive life.

It is a further object of the present invention to provide a method for forming an abrasive wheel wherein the abrasive granules or particles are removed during forming to the desired contour, without being crushed or multilated in any way.

It is a further object of the present invention to provide a method for forming an abrasive wheel wherein the abrasive particles, being retained about the periphery of the wheel in a resin or metal bond, drop out due to a removal of the bond about the particles.

It is a further object of the present invention to provide a method for forming an abrasive wheel wherein the abrasive particles, being retained about the periphery of the wheel in a resin or metal bond, drop out due to a removal of the bond about the particles by engagement with an abrasive lapping compound floating between the abrasive wheel and a lapping wheel.

It is a further object of the present invention to provide a method for forming an abrasive wheel which has an extended useful abrasive life wherein a grinding wheel having the desired cont-our and which may be of a carbide, aluminum oxide, etc., is employed to form a complementary contour in a lapping wheel, the lapping wheel then being employed to form the abrasive wheel by causing a mixture of a lapping compound to fioat therebetween during the forming operation, the abrasive particles then dropping from the abrasive wheel due to a removal of the binder retaining the particles on the periphery of the abrasive wheel.

It is a further object of the present invention to provide a method for forming an abrasive wheel which has extended useful abrasive life wherein a grinding wheel having the desired contour is formed from a template through a pantograph apparatus, the grinding wheel being then employed to form a complementary contour in a lapping wheel, the lapping wheel then being employed to form the abrasive wheel by causing a mixture of a lapping compound to float therebetween during the forming operation, the abrasive particles then dropping from the abrasive wheel due to a removal of the binder retaining the particles on the periphery of the abrasive wheel.

It is a still further object of the present invention to provide a method for forming a diamond wheel having a grit in the range of 80 to 320, which diamond wheel has an extended useful abrasive life and wherein an aluminum oxide grinding wheel having the desired contour is formed from a template through a pantograph apparatus, the grinding wheel then being employed to form a complementary contour in a lapping wheel, such as a wheel of cast iron, the lapping Wheel then being employed to form the diamond wheel by causing a mixture of a lapping compound to float therebetween during the forming operation, the diamond particles then dropping from the diamond wheel due to a removal of the binder retaining the diamonds on the periphery of the diamond wheel, the lapping compound being applied as a first mixture wherein the grit is in the range of 100 to 220 and a second mixture wherein the grit is in the range of 220 to 320.

These and other objects of the present invention are accomplished by forming a wheel of aluminum oxide, carbide, etc., into the desired contour of a diaforming apparatus, which apparatus employs a type of pantograph system. After the wheel, now known as a grinding wheel, has been properly contoured, it is positioned in a coplanar relationship to grind the periphery of a form lapping wheel, which may be of cast iron or the like, into the desired contour. Upon completion of the lapping wheel, which has a contour complementary to that of the grinding wheel and the final abrasive wheel, it is placed on a spindle for free rotation. The abrasive wheel, such as a diamond wheel, to be dressed is placed on a power-driven spindle for rotation which, for example, may be 160 revolutions per minute. A rough lapping grit is supplied by any convenient means, such as by a small brush, to the peripheral surfaces between the lapping wheel and the abrasive wheel to be formed. The lapping grit or medium is applied and the lapping wheel is moved toward the abrasive wheel until it is just made to rotate thereby. That is to say, the lapping wheel and the abrasive wheel are not necessarily in intimate contact but are in contact through the lapping compound. The abrasive Wheel is first shaped by means of the rough lapping grit applied to the lapping wheel after which it is finally shaped by means of a finishing grit. It is preferable that the form lapping wheel be much larger in diameter than the abrasive wheel being dressed. Thereafter, the contour of the abrasive wheel is checked by means, such as by optical means, to ascertain if it has reached the desired configuration.

It will be noted that the lapping wheel is not forced into crushing engagement with the abrasive wheel to be formed. Apparently, what takes place during the lapping of the final diamond wheel or wheel of other abrasive, is that the lapping grits employed as the lapping agent eat out and remove the resin or metal bond in which the diamonds or abrasive are retained upon the periphery of the abrasive wheel, which causes the diamonds 0r abrasive to be undermined so that they fall out and are removed in substantially the condition that they were when formed in the wheel. The diamonds or other abrasive material are not crushed or mutilated in any manner so as to cause their surfaces to become rounded, splintered, etc., or in any other way to decrease the useful tool life of the abrasive wheel.

After the abrasive wheel, such as the grinding wheel just formed, has been used for a period of time, such as for shaping tungsten carbide tools, it will again require dres ing by the lapping wheel as just set forth. After several such dressing operations, the lapping wheel will in turn require dressing by the grinding wheel. The grinding Wheel, in turn, will be periodically dressed to shape by means of the template employed in the diaforming apparatus.

The invention both as to its organization and method of operation together with further objects and advantages thereof will best be understood by reference to the following specification taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a step-by-step block diagram of the invention;

FIGURE 2 is a plan view showing the formation of the grinding wheel by the diaforming apparatus;

FIGURE 3 is a plan view showing the formation of the lapping wheel by the grinding wheel formed in the FIG- URE 2;

FIGURE 4 is a plan view showing the position of the lapping wheel and the abrasive wheel prior to the application of the lapping grits;

FIGURE 4A is an enlarged fragmentary view of a diamond wheel as received from the manufacturer and before its formation in accordance with the principles and teachings of the present invention;

FIGURE 5 is an end elevational view illustrating the application of the lapping compound to the wheels;

FIGURE 5A is an enlarged fragmentary view showing the interface between the wheels of the FIGURE 5;

FIGURE 6 is a plan view showing the formation of a chalk form which is inspected to check the accuracy of the contour of the abrasive wheel;

FIGURE 7 is a view illustrating the optical means used to inspect the chalk form produced in the FIGURE 6; and

FIGURE 8 is a sectional view of the finished abrasive wheel, such as a diamond wheel, ready for use.

With reference to the FIGURE 1, the steps of the process are set forth in the blocks 10, 12, 14, 16, 18, 20, 22, and 24, as shown. The step shown in each block is illustrated by apparatus of one of the figures, as indicated in the respective blocks. Reference will now be made to the corresponding figure which illustrates the respective step.

The first step illustrated in the block 10, is the diaforming of a grinding wheel, such as a grinding wheel of aluminum oxide or silicon carbide. This step is illustrated in detail with reference to the FIGURE 2. A template 26 has formed on one of its surfaces 28 the contour which is desired upon the finished abrasive wheel, such as the diamond wheel illustrated in later figures. The template 26 may be a full scale model or, to increase the accuracy of reproduction, the template 26 may be much larger than the finished abrasive wheel desired since it may be reproduced and reduced by a diaforming apparatus employing a type of pantograph 30 shown in the FIGURE 2. The apparatus in the FIGURE 2 is well known in the art and sufiice it to say, that the surface contours 28 of the template 26 are cut by a single diamond cutter into the periphery of a grinding wheel 32, which is mounted for rotation upon a shaft 34 and secured theerto.

After the grinding wheel 32 has been formed in accordance with the surface 28 of the template 26, the next step is illustrated in the block 12 of the FIGURE 1, i.e., form a lapping wheel, for example, as of cast iron or other material by engagement with the dressed grinding Wheel 32' produced in the FIGURE 2. The step illustrated in the block 12, is shown in the FIGURE 3. The grinding wheel 32, now illustrated in its formed or dressed state as 32, is mounted upon the shaft 34. A lapping wheel 36 is mounted for rotation upon a shaft 28. A power shaft 40 has a pulley 42 positioned substantially in line with a pulley 44, which is positioned upon an end of the shaft 38. Power is supplied from the pulley 42 to the pulley 44 via a belt 46. The grinding wheel 32' and the lapping wheel 36 are positioned substantially in line so that a complementary contour may lbB formed in the lapping wheel 36. The formation is accomplished through the rotation of the shaft 34 and 38 in opposite directions, as shown, or the shafts 34 and 38 may be rotated in the same direction as long as the peripheral velocities of the wheels 32 and 36 are not equal. However, preferably the wheels 32' and 36 are rotated in the directions shown. In this manner, a contour complementary to the contour of the grinding wheel 32' is formed upon the periphery of the lapping wheel 36. This complementary contour is illustrated as the lapping wheel 36' of the FIGURE 4.

The apparatus of the FIGURE 4 illustrates the step shown in the block 14 of the FIGURE 1, i.e., the formed lapping wheel 36 is set up and aligned with an abrasive wheel, such as a diamond abrasive wheel 48 illustrated in the FIGURE 4A. The abrasive wheel 48 of the FIGURE 4A is of the configuration such as it may be received from the manufacturer. The wheel comprises a center portion 50 of metal or other suitable material with a plurality of small diamonds 52 embedded in a thin layer of resin or metal bonding material 54.

The illustration and purpose of the apparatus in the FIGURE 4 is to form, by engagement with the lapping wheel 36, the abrasive wheel 48 in accordance with the peripheral contour of the lapping wheel 36. Since the lapping wheel 36' supports a contour complementary to that of the grinding wheel 32' of the FIGURE 3, the abrasive wheel 48 of the FIGURE 4 will now be formed having a peripheral configuration substantially identical to that of the grinding wheel 32. The abrasive wheel 48 is supported upon a shaft 56 to which rotational motion is supplied, in the direction shown.

Since the formation of the abrasive wheel 48 is to commence, the blocks 16 and 18 of the FIGURE 1 set forth the step of applying the rough lapping grit and the step of applying the finish lapping grit, respectively. The application of the lapping compound or grit is shown in the FIGURES 5 and 5A. The lapping wheel 36 is brought very close to the abrasive wheel 48 and a lapping grit applicator 58 of the FIGURE 5 applies an appropriate grit to the lapping wheel 36'. The lapping grit applicator 58 may be any of a well known type, such as a small brush, a pipe, etc. The lapping wheel 36' is moved toward the abrasive wheel 48 until rotation of the lapping wheel 36 commences. With reference to the FIGURE 5A, it will be noted that the lapping wheel 36' would not usually engage the periphery, which includes the diamonds 52 and the resin or other bonding material 54, of the abrasive wheel 48. However, contact is made through the lap ping compound 60 which includes the appropriate abrasive grit as well as a viscous material to cause its flow. As the shaping of the abrasive wheel 48 progresses, the lapping wheel 36 is periodically repositioned toward the abrasive wheel 48 until the final shape is achieved.

The grit sizes are in accordance with the sizes standardized by The grinding Wheel Manufacturers Association of the United States and Canada. The finer grades of grit have the higher numbers. For example, if an 80 grit diamond wheel is to be dressed, a grit roughing lapping grit and a 180 grit finishing lapping compound would preferably be used. For a or grit diamond wheel, 180 rough and 280 finish grit would preferably be used. For a 220 grit diamond wheel, 220 rough and 280 finish lapping grit would preferably be used. Grit varying from 100 to 320 is also used depending on finish required or grit size of the diamonds for lapping straight or flat faces or angles. These lapping grits work equally well on resin or metal bonded wheels.

It will be noted that the diamonds 52 of the abrasive wheel 48 are not crushed or forcibly removed from the resin or metal bonding material 54, in any way. The lapping grit or compound 60 cats out or removes the resin or bonding material 54 so that the diamonds 52 drop out intact. One such diamond is shown at 52' as leaving its bonding material 54 and being swept into the lapping compound 60. It will be noted that the diamond 52' is neither crushed nor rounded in any manner but is removed substantially intact. In this manner, the diamonds 52 which remain and form the surface of the abrasive wheel 48, remain sharp and thus provide the most abrasive surface possible. It will be intuitively clear that if the diamonds 52 are crushed and forcibly removed from their bonding material 54, then the remaining diamonds at the surface may be splintered, shattered, or rounded and in these conditions do not present as abrasive a surface as that surface presented by the practice of the present invention.

The block 20 of the FIGURE 1 illustrates the next step which is an inspection step wherein the abrasive wheel 48 is caused, in the FIGURE 6, to form a thin section of chalk 62 which is supported by and advanced by its holder 64. After the chalk 62 is formed, the next step is illustrated in the block 22 of the FIGURE 1 wherein the chalk form 62 is inspected to check the accuracy of the contour of the abrasive wheel 48'. This is illustrated in the FIGURE 7 wherein the chalk form 62 may be compared with a reference 66 in a comparator, such as a well known optical comparator illustrated at 68. The reference 66 of the FIGURE 7 may be the template 26 having the surface 28 of the FIGURE 2 or may be a reference formed therefrom.

If the contour on the chalk 62 compares satisfactorily with the reference 66 in the comparator 68 of the FIG- URE 7, then the abrasive wheel 48' is ready for use, as illustrated by the block 24 of the FIGURE 1 and the dressed abrasive wheel 48' of the FIGURE 8. The abrasive wheel 48 will now bear upon its periphery a contour 28' which is substantially identical to the contour or surface 28 of the template 26 of the FIGURE 2. It will be noted that the diamonds 52 remaining to form the abrasive surface of the wheel 48' are neither crushed, splintered nor rounded so that the practice of the invention produces an abrasive wheel, such as the diamond wheel having a highly abrasive surface and a long life. It will be understood that the number of diamonds 52 in the foregoing figures has been reduced for the purposes of clarity and that in an abrasive wheel, such as that illustrated in the figures, would literally contain hundreds of diamonds or other abrasive particles so as to present a substantially smooth and contoured outline, such as shown in the FIGURE 8.

The grit of the lapping compound 60 employed in the practice of the invention, is that as set forth. Understandably, the rough and finish grits will vary according to the grit of the abrasive wheel which is to be formed. The lapping compound 60 may be, for example, silicon carbide lapping grits in water. The grits move about the interface between the lapping wheel 36' and the abrasive wheel 48 forming chains between these wheels. The chains transmit cutting force to the grits in contact with the diamond carrying material or bonding material 54, causing the bonding material 54 to be eroded away. This action also creates a force to rotate the lapping wheel 36'. In this manner, the diamonds or other abrasive particles of the abrasive wheel are neither crushed nor mutilated in any way but are removed substantially intact due to the removal of the bonding material retaining them upon the surface of the wheel. The speed of rotation of the abrasive wheel 48 is variable; however, in the apparatus which was constructed and operated in accordance with the principles as taught by the present invention, the abrasive wheel 48 rotated at 160 revolutions per minute. Understandably, the abrasive wheel 48 and the lapping wheel 36' would not be of the same diameter so as to preclude the arrival of identical peripheral areas at successive revolutions.

It is to be understood that in accordance with the invention any desired shape may be formed into the abrasive wheel 48'. For example, if it is desired that the wheel 48 have a straight face parallel with its axis of rotation then a straight faced lapping Wheel 36 would be made by reciprocating a grinding wheel across its face. During the forming of the abrasive wheel the straight faced lapping wheel whose axis of rotation would be parallel to that of the abrasive wheel, would preferably be oscillated axially back and forth across the face of the abrasive wheel. Such a straight faced lapping wheel may also be employed for forming angles on portions of the side faces of the abrasive wheel that are adjacent the peripheral face. In such case the peripheral face of the lapping wheel is positioned at the proper angle with respect to the corner formed by the intersection of a side face and the peripheral face of the abrasive wheel. Here again, it is desirable to oscillate the lapping wheel axially as the lapping in of the abrasive wheel progresses. It is to be noted that the axis of the abrasive wheel and that of the lapping wheel will not be parallel during such a side facing operation. The straight faced lapping wheel can also be employed to form a stright faced abrasive wheel but with the face being at an angle to the axis of rotation. In such a forming operation the angle between the axis of the abrasive and lapping wheels is adjusted so that the desired angle will be formed on the face of the abrasive wheel as the face of the forming wheel is oscillated back and forth across the face of the abrasive wheel. Grooves may be formed in the face of the abrasive wheel by employing a lapping wheel of the proper width to form the desired groove width. Ledges and other shapes may be formed in the face of the abrasive wheel by means of a straight faced lapping wheel by manipulating the position of the lapping wheel with respect to the abrasive wheel as required.

Although examples of the material of which the various wheels may be constructed have been set forth, it will be understood that these are illustrative only and that other materials may be employed such as found expedient or necessary.

Thus, the present invention may be embodied in other specific forms without departing from the spirit and the essential characteristics of the invention. The present embodiment is, therefore, to be considered in all respects as illustrative and the scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of the equivalency of the claims are, therefore, intended to be embraced therein.

What is claimed is:

1. A method of forming a shaped contour in an abrasive wheel having abrasive particles held in a bonding material surfaced about its periphery; comprising the steps of rotating the abrasive wheel, positioning a form wheel having its periphery configured to a predetermined shape adjacent to the abrasive wheel, coating the periphery of said form wheel with a lapping compound, bringing the form wheel toward the abrasive wheel while maintaining a spaced relationship therebetween such that the rotary motion of the abrasive wheel is imparted to the form wheel through the lapping compound, whereby the lapping compound dislodges certain of the abrasive particles by a removal of the bonding material for forming said abrasive wheel to conform to the predetermined shape of the form wheel.

2. The method of claim 1 wherein the angular relationship between the axes of rotation of the abrasive wheel and the form wheel is maintained constant.

3. The method of claim 2 wherein said axes of rotation are substantially parallel.

4. The method of claim 1 wherein the form wheel is shaped by a grinding wheel having the predetermined shape of the finished abrasive wheel to be formed.

5. The method of claim 4 wherein said grinding wheel is shaped by a diaforming apparatus having a template formed with the contour desired upon the finished abrasive wheel.

6. The method of claim 1 wherein the said abrasive particles are diamonds having a grit in the range of to 320 and the said lapping compound is applied in two stages, the first stage being a rough lapping compound having a grit in the range of to 220 for the initial re- :moval of the bonding material and the second stage being a finish lapping compound having a grit in the range of 220 to 320 to finish the forming of the abrasive wheel.

7. A method of forming a shaped contour in an abrasive wheel comprising the steps of positioning a form wheel having a predetermined shape adjacent and out of engagement with the abrasive wheel, rotating one of the wheels, maintaining a constant angular relationship between the axes of rotation of both wheels, and transmitting rotational motion to the other one of said wheels from the rotated wheel through a lapping compound for forming the abrasive wheel in accordance with the shape of the form Wheel.

8. The method of claim 7 wherein the form wheel is shaped by a grinding wheel having the predetermined shape of the finished abrasive wheel to be formed.

9. The method of claim 8 wherein said grinding wheel is shaped by a diaforrning apparatus having a template formed with the contour desired upon the finished abrasive wheel.

10. The method of claim 7 wherein the abrasive wheel has diamond particles having a grit in the range of 80 to 320 and the said lapping compound is applied in two st-ages, the first stage being a rough lapping compound having a grit in the range of 100 to 220 and the second stage being a finish lapping compound having a grit in the range of 220 to 320 to finish the forming of the abrasive wheel.

References Cited UNITED STATES PATENTS 2,731,336 1/1956 Wallace et al. 51-309 2,863,750 12/1958 Booth 51-293 3,212,869 10/ 1965 Decker 51298 DONALD J. ARNOLD, Primary Examiner.

US. Cl. X.R. 51-298, 309 

